Batteries based on lithium (Li), such as lithium-ion batteries, are attractive due to their high energy density compared to other commercial batteries. Lithium-ion batteries are used commercially in computers, cell phones, and related devices. Battery lifetime is often a critical factor in the marketplace, especially for commercial, military, and aerospace applications. Battery life is often the limiting factor in many aerospace products, such as satellites.
Lithium-ion batteries have potential for use in electric vehicle/hybrid-electric vehicle (EV/HEV) applications. In recent years, commercial efforts have attempted to improve lithium-ion batteries to meet the requirements demanded for target applications. Particularly for EV/HEV applications, long cycle life is a critical requirement. Presently, this requirement has not been met.
Previous methods of extending battery life include employing long-life cathode and anode materials, and restricting battery operation to avoid conditions detrimental to battery life. Examples of such conditions include high and low temperatures, high depths of discharge, and high rates. These restrictions invariably lead to under-utilization of the battery, thus lowering its effective energy density. In addition, precise control of cell temperature with aggressive thermal management on the pack level is usually required, which adds significantly to system weight, volume, and cost. Even with these operation and design restrictions, battery life is still limited to at most a few thousand cycles.
In light of these and other shortcomings in the art, improved battery structures are needed. What is needed is a low-cost approach to increase the calendar and cycle lifetimes of lithium-ion batteries, while maintaining full utilization of the battery. Improved batteries should offer equal or higher energy density compared to state-of-the-art batteries, while preferably having longer cycle and calendar lifetimes by including means for reviving and restoring capacity.